This is a solid, dark treatment of the license, the full game is more polished than the demo (which itself was a good concantenation of a few segments of the game to show scope and diversity), the detective mode has been tweaked (and is pretty slick), the art direction is cool (and consistent), fanboy unlockables are solid and slickly implemented, and I like the progression, the open-endedness(ish)ism of the title. And (yay!) the video tweak settings let me brighten the game without washing out the graphics -- very important for playing on a projector.
Mark Hamill (who is the Joker) and Kevin Conroy (who is the Batman, at least until I am), are fantastic -- as is a lot of the primary voice acting (some of the secondary (like the guards) doesn't come close to the caliber, which is unfortunate). Good voice acting makes a game; bad kills it. This is stellar stuff.
And I like that there are subtle things like me being able to move Batman around during an in-engine cutscene, downed enemies are still breathing (they're unconscious, not dead), and the brief (at least one so far) first-person implementation (hey, you get it for free with the tech; might as well play with it; which most licensed fair refuses to do).
It's got a few shortcomings, but nothing that kills the game for me.
First off is I'm not crazy about the muscle-bound nature of ol' Bats -- feels a bit over-done, put - a -space -marine - in - a - batsuit. Also, the skinning of the game is a bit of a weird mix of shiny and muddy, but that's stereotypical of the Unreal Engine (right or wrong). Also, I'm sure I'm in the minority, but I game on a projector, and at that size Rocksteady's particular implementation of the third-person camera causes a bit of a problem with slight queasiness that most other games don't cause.
But overall, the game is solid, I'm enjoying it, kudos to Rocksteady for getting it right, and I'll be tooling through it for a while.